LAFAYETTE, Colo. (CBS4) – Police evacuated a high school in Lafayette Monday morning after an explosive device was found.

Police closed South Boulder Road after 9 a.m. after a suspicious bag was spotted on the campus of Centaurus High School. Students were sent home for the day while the bomb squad investigated.

A faculty member spotted the brown paper bag inside the school on the north side of the building, describing it as something that “could have looked like a bomb.” The teacher then put the device outside. Inside the bag authorities found what they believed was a suspicious-looking device and the Boulder County Bomb Squad was called in.

On Monday evening authorities confirmed to CBS4 the device was in fact a real explosive. The bomb squad had successfully detonated the device just after noon.

There were rumors that multiple devices had been found on the campus, but authorities said that wasn’t true. The police presence for so many hours, including the FBI, had people in the neighborhood concerned.

Some students said they didn’t know initially if it was a prank at the school because it’s the last week of classes or if it was more of a concern.

(credit: CBS)

“We were guided into the parking lot at which point, about 10 minutes later guided back towards the football fields and the whole school was on the football fields,” student Kristine Huth said.

“Officer Wendy said, ‘You can go home, school is out, but you can’t get your cars. You have to walk wherever you’re going. If you live close, just go to your friend’s house and just hang out if you have any friends close to the school and just hang out there because school is gone,’ ” student Rachel Bacon said.

Students were allowed back on campus to pick up their vehicles Monday evening. Police said they are taking the situation very seriously.

“Especially with recent events that have happened throughout the nation, especially in our schools. We don’t take it lightly, so we’ve got everything shut down, we’re taking it seriously,” Sgt. Peter Voris with the Lafayette Police Department said.

Authorities told CBS4 they planned to remain at the school well into the evening, but school officials said there will be class on Tuesday.